Author Topic: Mk 5 ignition  (Read 3100 times)

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Offline ERIC BAYLISS

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Mk 5 ignition
« on: 24 Feb 2013 at 11:56 »
 Good morning lads, while I have got the cylinder head of to change a blown gasket on my Mk5 I want to check the ignition timing but dont want to disturbe the timing cover to use a timing disc on the crank and then find every thing is ok, can any one tell me how far the piston should be from TDC with the ignition fully advanced. thank you.  eric

Offline eddie

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Re: Mk 5 ignition
« Reply #1 on: 24 Feb 2013 at 17:23 »
Eric,
        Mr Douglas only ever gave the ignition advance as 36 degrees before TDC, fully advanced, but by my calculations, that works out at .276" before TDC.

   Regards,
                  Eddie.

Offline ERIC BAYLISS

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Re: Mk 5 ignition
« Reply #2 on: 24 Feb 2013 at 20:34 »
 Thanks Eddie, thought you would have an answer.

Offline ERIC BAYLISS

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Re: Mk 5 ignition
« Reply #3 on: 03 Mar 2013 at 12:32 »
 On checking the ignition I found it was out, but I also found that with it fully retarded I get a lovely big spark if you advance it on the lever the spark gets weaker till it stops altogether.has any one got any bright ideas.the only thing I can think of is that the points may have come out of a single instead of a twin.they were already in this mag when    I bought it to put on this engine so it has not been on the road yet.

Offline eddie

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Re: Mk 5 ignition
« Reply #4 on: 03 Mar 2013 at 13:12 »
Eric,
        The points are the same for single and twin magnetos, but there are 2 types for left or right hand rotation. When viewed from the points end, the mag for a Mark rotates anti clockwise. The heel on the points should trail the pivot - if it leads the pivot, you have the wrong hand points assembly. Also, the slipring that the HT brushes bear on can also be left or right handed - the difference is the position of the brass segment - it should start about midway between the poles of the armature, and be trailing when the armature is turned in the normal direction. If the points are wrong, the spark will not occur at the point of maximum flux. If the slipring is of the wrong rotation, a good spark may be occurring but when the brass segment is some way from the HT brushes. Left and right hand cam rings are also available but it is unlikely this is the cause as they can only be fitted in the matching end plate.
  If you remove the dynamo, you should be able to turn the magneto slowly and feel the pull of the magnets - the points should open just as or just after the pull eases. This will determine whether the points are opening at the correct time. Having checked this, remove the HT pickups and look at the brass segment in the slipring - with the points just opening, it should have just come into line with the brush, with the rest trailing when the mag is turned in it's normal direction. If the brass segment is ahead of this, the slipring is for the wrong direction.
 These checks should be done with the mag fully advanced - on a Mark, with the advance/retard cable tight.
   If all this checks out and you still have a weak spark, I fear a rewind and new condenser will be needed.

   Regards,
                  Eddie.
   Hope some of this helps

Offline ERIC BAYLISS

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Re: Mk 5 ignition
« Reply #5 on: 03 Mar 2013 at 17:09 »
 Thanks again Eddie, they are the wrong points,  just checked and the heel leeds.that also explains why the ignition was fixed fully retarded when I bought the mag.just need to find the correct ones now.   eric

 

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